The present invention relates to an environmentally safe cleaning process for removal of contaminants from a substrate surface which employs a water rinse whereby the water is reused. Also the present invention relates to a cleaning composition useful in such process.
A number of patents are directed to removal of contaminants from specific substrate surfaces.
Dean U.S. Pat. No. 4,673,524 discloses a cleaner suitable for cleaning hands and difficulty removable objectionable material such as modern catalyzed auto paint, fast drying printers ink by use of a multicomponent composition containing 25-65% by weight of a dibasic ester admixture of dimethyl succinate, dimethyl glutarate and dimethyl adipate, 5-25% by weight dipropylene glycol methyl ether, 5-25% by weight odorless mineral spirits, 4-9% by weight triethanolamine, 5-15% by weight octylphenoxypolyethoxyethanol, 1-3% by weight nonyl phenol ethoxylate and 8-18% by weight tall oil fatty acid.
Jackson U.S. Pat. No. 4,780,235 discloses a low toxicity paint remover composition containing C.sub.1 to C.sub.4 dialkyl esters of C.sub.4 to C.sub.6 aliphatic dibasic acid, an activator, a thickener, a surfactant and at least one other organic nonhalogen-containing solvent.
Hayes et al. U.S. Pat. No. 4,640,719 discloses use of terpene compounds in cleaning printed writing boards. This patent discloses cleaning of residual flux and particularly rosin solder flux and adhesive tape residues employing terpene compounds such as pinene including its alpha and beta isomer, gamma terpinene, delta-3-carene, limonene and dipentene with limonene and dipentene preferred. Dipentene is the racemic mixture of the limonene optically active isomers. This patent further discloses that these terpene compounds are almost completely insoluble in water and cannot be directly flushed away by water. Therefore in a preferred embodiment terpene compounds are combined with one or more emulsifying surfactants capable of emulsifying terpenes with water to facilitate their removal.
Dishart et al. U.S. Pat. No. 4,867,800 discloses cleaning of printed circuit board substrates with a combination of a dibasic ester and terpene.
Futch et al. U.S. Pat. No. 4,934,391 discloses removal of rosin solder flux or resist residues employing a dibasic ester and an emulsifying surfactant. In a distinct embodiment, a combination of terpenes and dibasic esters are disclosed.
With the advent of tightened restrictions on the use of CFCs and chlorocarbon solvents, metal fabricators and other manufacturers are faced with a choice among many options for satisfying their cleaning requirements. These include flammable alcohols, high-flash-point solvents, semi-aqueous cleaners based on terpenes or terpenes/dibasic esters, and aqueous cleaners. Alcohols clean well but are flammable, high-flash-point solvents leave residues which are slow drying, terpenes have undesirably low flash points and objectionable odors, dibasic esters are a poor solvent for oils and greases, and aqueous cleaners are ineffective for removing heavy oils and greases from tight clearances. In addition aqueous and semi-aqueous cleaners pose waste disposal problems unless the soils removed can be effectively separated from the waste water.
A need exists for a semi-aqueous cleaner which is effective for contaminant removal such as oil and grease, biodegradable, low in toxicity, readily separates from rinse water, has a mild odor and high flash point.